The invention relates to a device for depositing in particular crystalline layers on in particular crystalline substrates, having a process chamber which is disposed in a reactor housing and the base of which carries at least one substrate holder, which is carried on a gas cushion in a bearing recess and is driven in rotation by the gas stream which maintains the gas cushion and flows through a feed line associated with the base.
Devices of this type are used, for example, to deposit semiconductor layers from the vapor phase by means of reaction gases fed to the substrate. At least the base of the process chamber is heated, so that the reaction gases decompose in the vapor phase which is heated as a result of the process chamber wall heating, and the decomposition products condense on the substrate. WO 96/23913 has disclosed, for example, a device for the epitaxial growth of silicon carbide, in which the process chamber is formed by a graphite tube which is heated using high frequency. It is known from this document for the substrate not to be placed directly onto the process chamber base, but rather onto a plate which rests on the base.
U.S. Pat. No. 6,039,812 A has likewise already disclosed a CVD reactor for deposition of silicon carbide. In this case, the entry to the process chamber is connected to a gas inlet system by means of a tube.
U.S. Pat. No. 4,961,399 shows a CVD rector with substrate holder which is mounted rotatably on a gas cushion and is driven in rotation by the gas stream. In this case, the process chamber is disposed as a cylinder symmetrically around a gas inlet element. In this case, there is a total of five rotatable substrate holders.
The invention is based on the object of technologically developing the concept of the substrate holder mounted rotatably on a gas stream in particular in a linear-flow process chamber.
The object is achieved by the invention given in the claims.
Claim 1 provides, firstly and substantially, that the bearing recess is associated with a tray disposed above the outlet opening of the feed line. In the case of a tunnel-like, linear-flow reactor, this tray can be removed on one side, in particular through the downstream opening in the process chamber, in order to change the substrate on the substrate holder. In a preferred development of the invention, there is provision for the tray to be equipped with an annular bead. This annular bead faces downward. Within the region surrounded by the annular bead it is preferable for there to be passage openings, through which the gas which carries the substrate holder and drives it in rotation can flow. This annular bead is preferably located in an annular groove associated with a step of the process chamber base. This ensures automatic centering and holding of the tray in the step of the process chamber base. The annular bead, which preferably tapers to a sharp edge, bears against the base of the annular groove in such a manner as to form a seal, so that a closed volume is formed between the surface of the step and the underside of the tray, into which volume the opening of the feed line opens out. This volume is used to distribute the gas of the gas stream flowing through the opening to a multiplicity of passage openings, which open out, in a known way, in helical grooves in the base of the bearing recess, in order in this way to bearingly support the substrate holder and drive it in rotation. The feed line preferably runs inside a graphite body which forms the base. The feed line preferably begins below the upstream process chamber opening, so that there are two openings disposed above one another, to which gas inlet tubes can be connected in order to feed the reaction gases into the process chamber and an inert gas from the feed line. These two pipelines run parallel to one another and originate from a common gas inlet member.
An independent inventive development of the device of the generic type provides that the base is formed by a cavity section of an in particular multipart graphite tube which has a substantially rectangular internal cross-sectional profile, a gas inlet element for one or more reaction gases being associated with the first tube end, and the second tube end forming a loading opening for the process chamber, and a reaction-gas inlet tube leading from the gas inlet member to the end-side opening of the process chamber, and a separate tube leading from the gas inlet member to the feed line opening below it.
The invention also relates to a method for depositing in particular silicon carbide by means of metal-organic compounds which have been converted to the vapor phase. According to the invention, it is provided that a tray is disposed in the process chamber. This tray is removable in order for the process chamber to be loaded with the substrates and for the substrates to be unloaded from the process chamber.